1. Field of the Invention
The present invention relates to a near-field light generating element that records and reproduces a variety of information on a magnetic recording medium using a near-field light with focused light flux, a near-field light head, and an information recording and reproducing device.
2. Background Art
In recent years, along with an increase in capacity of a hard disk or the like in computer equipment, the recording density of information in a single recording surface has increased. For example, in order to increase the recording capacity of a magnetic disk per unit area, there is a need to increase the surface recording density. Incidentally, as the recording density increases, the recording area occupied per bit on the recording medium is reduced. When the bit size is reduced, energy held by one bit of information comes close to the heat energy of room temperature, whereby there is a problem of thermal demagnetization in which the recorded information is reversed or disappears owing to thermal fluctuations or the like.
Although the in-plane recording method generally used is a method of recording the magnetism so that a direction of magnetization faces the in-plane direction of the recording medium, in this method, the recording information is easily lost due to the thermal demagnetization mentioned above. Thus, in order to solve this disadvantage, in recent years, a perpendicular recording method has been adopted in which a magnetization signal is recorded in a direction perpendicular to the recording medium. This method is to record the magnetic information using the principle of causing a single magnetic pole to approach the recording medium. According to this method, the recording magnetic field faces a direction that is substantially perpendicular to a recording film. Since it is difficult to form a loop with N-pole and S-pole within the recording film surface, information recorded in the perpendicular magnetic field is easily maintained energetically stably. For that reason, the perpendicular recording method becomes resistant to the thermal demagnetization compared to the in-plane recording method.
However, recent recording media require further increasing high densities in response to the needs for performing the recording and reproducing of larger amounts and higher densities of information, or the like. For that reason, in order to suppress the influence between the adjacent magnetic domains or the thermal fluctuations to the minimum, recording media having strong coercive force have begun to be adopted. For that reason, even in the perpendicular recording method mentioned above, it is difficult to record information on the recording medium.
Thus, in order to solve the disadvantage mentioned above, a hybrid magnetic recording type recording and reproducing head is provided in which the magnetic domain is locally heated using a spot light with focused light or near-field light to temporarily lower the coercive force, thereby performing the writing onto the recording medium in the meanwhile.
Among such recording and reproducing heads, a recording and reproducing head (a near-field light head) using the near-field light mainly includes a slider, a recording element having a main magnetic pole and an return pole that are placed on the slider, a near-field light generating element that generates the near-field light from the irradiated laser beam, a laser beam source that irradiates a laser beam toward the near-field light generating element, and an optical waveguide that guides the laser beam generated from the laser beam source to the near-field light generating element (for example, see JP-A-2008-152897). The near-field light generating element has a core that propagates laser beam while reflecting the same, a light flux propagation element having a cladding that comes into close contact with the core and seals the core, and a metal film that is placed between the core and the cladding to generate the near-field light from the laser beam. The core is drawn so that the cross-sectional area perpendicular to the propagation direction of laser beam facing from one end side (a light incident side) to the other end side (a light emission side) is gradually reduced, and is configured so as to propagate the laser beam toward the other end side while focusing the same. Moreover, the metal film mentioned above is placed on a side surface of the other end side in the core.
In the case of using the recording and reproducing head configured in this manner, a variety of information is recorded on the recording medium by generating the near-field light and applying the recording magnetic field. That is, a laser beam emitted from the laser beam source is incident to the light flux propagation element via the optical waveguide. Moreover, the laser beam incident to the light flux propagation element propagates through the cores and reaches the metal film. Then, since free electrons within the metal film are uniformly vibrated by the laser beam, Plasmon is excited and generates the near-field light on the other end side of the core in the state of being localized. As a result, the magnetic recording layer of the magnetic recording medium is locally heated by the near-field light and coercive force is temporarily lowered.
Furthermore, by providing the driving electric current to the recording element simultaneously with the irradiation of the laser beam mentioned above, the recording magnetic field is locally applied to the magnetic recording layer of the magnetic recording medium adjacent to the tip of the main magnetic pole. As a result, it is possible to record a variety of information on the magnetic recording layer in which the coercive force is temporarily lowered. That is, by the cooperation of the near-field light with magnetic field, the recording to the magnetic recording medium can be performed.